Are the Words Really Powerful?

Post moderns have taken biological motivation, let's call it the motivation for power at least, and sneaked it through the back door. It seems to me like a mask for the continuation of a marxs move under a new guise. We should be able to say our cog capacities are a power that we have, and they are a tool. And the whole point of using that tool is to increase our power in the world to achieve our goals. But another part of the post modern scepticism is to say that we cannot ground any values objectively. Instead, values are merely subjective preferences, either individually or group oriented.